The present invention relates generally to electrophotographic printing in image forming systems, and specifically relates to liquid immersion development of color prints.
Electrophotographic systems employing liquid immersion development (LID) technologies are well known. These types of systems typically include an image bearing member or photoreceptor having an image bearing surface on which latent images are formed and developed as single color or multiple color toner images for eventual transfer to a receiver substrate or copy sheet. Such electrophotographic systems also include a development station that utilizes a liquid developer material typically having about 2 percent by weight of charged, solid particulate toner material of a particular color, that is dispersed at a desired concentration in a clear liquid carrier.
In the electrophotographic process of a LID system, the latent images formed on the image bearing surface of the image bearing member or photoreceptor are developed with the charged toner particles, with excess liquid carrier being left behind or removed such that the developed images typically each contain about 12 percent by weight of the toner particles. The developed image or images on the image-bearing member are then further conditioned and subsequently electrostatically transferred from the image-bearing surface to an intermediate transfer member. Following that, the conditioned image or images are then hot or heat transferred from the intermediate transfer member, at a heated transfer or transfix nip, to an output image receiver substrate or copy sheet.
The ink or liquid developer material in conventional LID systems is about 2% solids (by weight) and developed images are on the order of 10%-15% solids (by weight). Such LID systems also include a biased metering roll for metering an amount of carrier fluid in the ink as well as for developing images with the metered ink. Fluid metering as such, and image development, are conventionally carried out separately, and typically by using a reverse rolling or moving metering roll.
LID systems typically also condition the initial ink developed image to provide increased image stability by conditioning the toner before it is transferred to the development station. Such conditioning is often achieved in conditioning stations that are supplied toner by a replenishing source.
LID systems utilize a technology known as xe2x80x9cpantoning.xe2x80x9d This process develops images using LID Pantone(copyright) inks. By mixing fourteen Pantone(copyright) basic colors, over a thousand colors can be achieved for producing high-quality prints. This ability to print Pantone(copyright) colors or Pantone(copyright) inks is one of the desirable features of liquid ink electro-photography. In addition, the use of a wet instead of a dry toner in LID systems produces high quality prints, and is especially useful in short-run productions where the use of some lithographic techniques are cost prohibitive.
To obtain high-quality prints having a Pantone(copyright) color, the toning process combines development, ink application, sump management, and control hardware and methodology. However, because of intrinsic properties of the Pantone(copyright) ink, the toned color produced by the development hardware can deviate from the expected print color if conventional toning processes are used. In particular, colors of the final print may not resemble those intended, resulting in poor quality prints.
Systems and methods are described herein for implementing a toning process designed to minimize and stabilize color deviation on a substrate, since conventional LID toning processes are not enough to deliver a robust product. Described below is a toning process that incorporates a toner conditioning station, which enables robust Pantone(copyright) prints, while significantly reducing the setup time required by the toning process.
For an effective and robust pantoning process, an ink conditioning station is described herein. The device establishes the proper mixture for any Pantone ink with the aid of an additional plate-out or drawing device and calorimeter before the ink is applied to the development station.
The ink conditioning station, which is designed and optimized to provide a quick setup and generate minimum waste, can be coupled with calorimeters and feedback control to allow automatic switching between the setup mode and the operational mode.
The ink conditioning station, which is designed and used in the setup mode, can also be operated in the operational mode with continuous plate-out and color monitoring. It therefore can serve the function of on-the-fly ink conditioning to maintain the ink stability if any disturbance occurs.
The Pantone mixture is established and maintained in the ink conditioning station. This Pantone mixture is different than the mixture of the toned images and the replenishing Pantone mixture. In one embodiment, the Pantone mixture can be prepared and poured into the conditioning station according to a pre-determined recipe.
The Pantone mixture, maintained in the Pantone ink replenishing source, has the same color mixture as the intent print color. The Pantone mixture is directed to the ink conditioning station. Once equilibrium is established and the toning process starts, little waste is generated.
The conditioned premix is manufactured along with the corresponding Pantone mixture for printing, and can be provided to the customers (in relatively small amounts) together with the given Pantone mixture. Such a use of the premix allows an instant setup with little waste.
In particular, an image forming system for producing an image of a desired color on a substrate is described herein. The system includes a conditioning station for conditioning a toner prior to forming the image on the substrate, and a drawing device to draw a portion of the toner from the conditioning station. The system also includes a control device coupled to the drawing device for sending a signal to form the image on the substrate if the drawn toner is suitable for producing the desired color.
Also described herein is a method for producing an image of a desired color on a substrate. The method includes filling a conditioning station with a toner, and drawing a portion of the toner from the conditioning station. Subsequently, the portion of the toner is analyzed to determine whether the toner is suitable for producing the desired color. Then, provided the toner is suitable for producing the desired color, the toner is fed to a development station for producing the image of the desired color on the substrate.